# HG changeset patch
# User Oleksandr Gavenko <gavenkoa@gmail.com>
# Date 1581593442 -7200
# Node ID 3a97cc7e1b39b805faf44702ee949e172f1849d0
# Parent  6163ed9ff6de47c4fef6c16931c4221a27b25ee9
About monit.

diff -r 6163ed9ff6de -r 3a97cc7e1b39 monit.rst
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/monit.rst	Thu Feb 13 13:30:42 2020 +0200
@@ -0,0 +1,193 @@
+
+=======
+ monit
+=======
+.. contents::
+   :local:
+
+Official docs
+=============
+
+https://mmonit.com/monit/documentation/monit.html
+  Main docs.
+https://mmonit.com/wiki/Monit/ConfigurationExamples
+  Real-world configuration examples.
+https://mmonit.com/wiki/Monit/FAQ
+  FAQ
+
+Debugging monit
+===============
+
+Run standalone::
+
+  monit -c /path/to/monitrc
+
+Check syntax::
+
+  monit -t
+  monit -t -c /path/to/monitrc
+
+Override log file location in config::
+
+  set log /var/log/monit.log
+
+or with CLI option::
+
+  monit -l /var/log/monit.log
+
+Do not go into background::
+
+  monit -I
+
+Make verbose output::
+
+  monit -v
+  monit -vv
+
+Full length commant may look like::
+
+  sudo monit -v status
+  sudo monit -Iv validate
+  sudo monit -Ivv -c /path/to/monitrc
+
+To debug start/stop scripts write wrapper that redirects STDIO to file::
+
+  #/bin/sh
+  exec 1>my.log
+  exec 2>my.log
+  echo "$@"
+  exec "$@"
+Limiting server to ``localhost``::
+
+  set httpd port 2812
+    use address localhost
+    allow localhost
+    allow admin:monit
+
+Monit modes
+===========
+
+* In ``active`` mode (the default), Monit will pro-actively monitor a service and in case of
+problems raise alerts and/or restart the service.
+* In ``passive`` mode, Monit will passively monitor a service and will raise alerts, but will not
+try to fix a problem by executing start, stop or restart.
+* In ``manual`` mode, Monit will enter active mode only if a service was started via Monit.
+
+Example::
+
+  check process App with pidfile /var/run/app.pid
+    start program = "/usr/bin/app start"
+    stop program = "/usr/bin/app stop"
+    mode passive
+
+Alerting
+========
+::
+
+  check process memcached with match memcached
+    start program = "/usr/bin/systemctl start memcached"
+    stop program = "/usr/bin/systemctl stop memcached"
+    if failed host 127.0.0.1 port 11211 protocol MEMCACHE then restart
+    if cpu > 70% for 2 cycles then alert
+    if cpu > 98% for 5 cycles then restart
+    if 2 restarts within 3 cycles then timeout
+
+  check process myapp with pidfile /run/myapp.pid
+    if does not exist then alert
+
+  check filesystem Ubuntu with path /dev/sda1
+    if space usage > 90% then alert
+  check filesystem Home with path /dev/sda3
+    if space usage > 90% then alert
+
+  check host app_name with address 127.0.0.1
+    start "/sbin/start app_name"
+    stop "/sbin/stop app_name"
+    if failed port 80 protocol HTTP
+      request /ok
+      with timeout 5 seconds
+      then restart
+
+Running monit by systemd
+========================
+::
+
+  [Unit]
+  Description=Pro-active monitoring utility for unix systems
+  After=network.target
+  Documentation=man:monit(1) https://mmonit.com/wiki/Monit/HowTo
+
+  [Service]
+  Type=simple
+  KillMode=process
+  ExecStart=/usr/local/bin/monit -I
+  ExecStop=/usr/local/bin/monit quit
+  ExecReload=/usr/local/bin/monit reload
+  Restart = on-abnormal
+  StandardOutput=null
+
+  [Install]
+  WantedBy=multi-user.target
+
+https://mmonit.com/wiki/Monit/Systemd
+  Official docs.
+
+Monitor systemd process
+=======================
+
+With pid-file::
+
+  check process nginx with pidfile /var/run/nginx.pid
+    start program = "/bin/systemctl start nginx"
+    stop program = "/bin/systemctl stop nginx"
+
+If process without pid-file::
+
+  check program MyApp with path "systemctl --quiet is-active MyApp"
+    if status != 0 then ...
+
+There is a way to tell systemd to create pid-file if process doesn't to it itself::
+
+  ExecStartPost=/bin/sh -c "echo $MAINPID > /run/myapp.pid"
+
+By matching program name::
+
+  check process MyApp matching 'myapp.*'
+     start program = /bin/app
+     stop program = something..
+
+Can systemd replace monit?
+==========================
+
+No. Systemd has only basic check if process is running. Imaging that process is stuck. You need some
+active probes, like HTTP health endpoint.
+
+Systemd has limited capabilities for notifying with ``OnFailure``::
+
+  [Service]
+  Restart=always
+  RestartSecs=30
+
+  [Unit]
+  OnFailure=...
+
+Reverse proxy for monit
+=======================
+
+Ngnix::
+
+  server {
+    listen   80;
+    server_name  my.server.name;
+    location /monit/ {
+      allow 127.0.0.1;
+      allow 192.0.0.0/8;
+      deny all;
+
+      proxy_pass http://127.0.0.1:2812;
+      proxy_set_header Host $host;
+      rewrite ^/monit/(.*) /$1 break;
+      proxy_ignore_client_abort on;
+    }
+  }
+